Hydro-mechanical steering differential systems are popularly employed in large track-type tractors and the like to provide smooth, equal and uninterrupted power and torque flow to both tracks at all times, including turns. A hydro-mechanical steering differential system is powered by a mechanical input and a hydraulic input. The mechanical input is typically from the transmission, while the hydraulic input is received from an engine driven variable displacement pump. One such hydro-mechanical steering differential is disclosed in U.S. Pat. No. 4,434,680 for a Planetary Steering Differential, issued Mar. 6, 1984 to Craig W. Riediger, et al and assigned to the assignee hereof. Such patent discloses the use of three separate planetary mechanisms. While suitable for large tractors, the three planetary mechanisms make the system not only complex and costly, it requires a large amount of space to contain all of the components.
Thus what is desired is a truly compact hydro-mechanical steering differential which is less complex, less costly and adaptable to smaller tractors.
The present invention is directed to overcoming the shortcomings of the prior attempts at providing a such a hydro-mechanical steering differential for smaller tractors.